Synthesis of biurets and isocyanates with alkoxysilane functions, formulations containing same and use thereof

ABSTRACT

The invention relates to a composition and a method of preparing one such composition and an isocyanatoalkoxysilane; the polyisocyanate composition contains at least two different oligomeric compounds comprising at least three units and at most five units selected from aminoalkylsilane units and diamine units and at least one function selected from isocyanate functions and from those derived therefrom, the aforementioned compounds having at least two aminoalkylsilane units and another compound having at least two diamine units; the invention is suitable for coatings.

This application is an application under 35 U.S.C. Section 371 ofInternational Application Number PCT/FR2004/003261 filed on Dec. 16,2004.

A subject matter of the present invention is polyisocyanate compositionsexhibiting silane functional groups and in particular alkoxysilanefunctional groups, the preparation of these compositions and the use ofthese compositions. Another subject matter of the invention is thesynthesis of monomers comprising both a silane functional group and anisocyanate functional group.

In order to place the present invention in industrial and semanticcontext, it is advisable to restate a certain number of points and tospecify or recall a certain number of definitions.

Predominantly, polyisocyanate compositions are generally formed fromderivatives resulting from the oligocondensation of individual di-,tri-, indeed even tetraisocyanate molecule(s).

Such a type of molecule is described as “monomers” and is capable ofbeing obtained by phosgenation of a di(primary amine), optionallycarrying one, indeed even two, other primary amine functional groups.Thus, such a molecule comprises a unit composed of a carbon chaincarrying at least two nitrogens (originating from the diamine to bephosgenated), which unit will be denoted by “diamino unit” in thecontinuation of the description. The diamino unit serves here asvestiges or mark of the existence, past or present, of an isocyanatemonomer: thus, the diamino unit has the structure>N—R—N<where R represents a hydrocarbon radical which is the residue of anisocyanate monomer, after ignoring two isocyanate functional groups. Ofcourse, R does not exhibit any of the functional groups created duringoligomerization of an isocyanate functional group, namely the carbamate,urea (including biuret), allophanate or biuret functional groups andthose which are mentioned on the occasion of the description of theoligocondensation (including oligomerization). The molecular weight of—R— is at most equal to 200. R can comprise another “amino” group in thecase of the trifunctional monomers, such as LTI, NTI and UTI.

The “amino” symbols N< and >N mean that the nitrogen can be insertedinto any functional group, such as isocyanate, amine, amide, imide orurea functional group, and in particular the functional groups generatedby the oligomerization reactions.

These diamino units are found in virtually all of the oligocondensationsand in the vast majority of the conversions of the isocyanate functionalgroups. This observation makes it possible to refer to the number ofdiamino units in order to indicate in particular the state ofcondensation of the oligocondensates (including oligomers), indeed evenof the polycondensates, and even in the case of heterocondensates (inwhich cases, it is possible to have several types of diamino units).

According to the usage common in chemistry, when a functional group hasgiven its name to a family of compounds, as is the case for theisocyanates, the aromatic or aliphatic nature is defined according tothe point of attachment of the functional group under consideration.When an isocyanate is situated on a carbon of aliphatic nature, then theisocyanate compound is itself considered to be of aliphatic nature.Likewise, when an isocyanate functional group is attached to thebackbone via a carbon of aromatic nature, then the whole monomer will bedenoted by the expression “aromatic isocyanate”.

To clarify this point, it may be restated that:

-   -   any isocyanate functional group having a point of attachment        which is a member of an aromatic ring is regarded as aromatic;    -   any isocyanate functional group having a point of attachment (of        the nitrogen, of course) which is a carbon of sp³ hybridization        is regarded as aliphatic.

The following distinctions may be made among aliphatic isocyanates:

-   -   Any aliphatic isocyanate functional group having a point of        attachment separated from the closest ring by at most one carbon        (it is even preferably directly connected to it) is regarded as        cycloaliphatic.    -   Any isocyanate functional group having a point of attachment        carried by a secondary sp³ carbon (that is to say, a carbon        connected to two carbons and to a hydrogen) is regarded as        secondary.

Any isocyanate functional group having a point of attachment carried bya tertiary sp³ carbon (that is to say, a carbon connected to threecarbons) is regarded as tertiary.

-   -   Any isocyanate functional group having a point of attachment        carried by an sp³ carbon itself carried by a tertiary carbon        (that is to say, not taking into account the final bond, a        carbon connected to three carbons) is regarded as neopentylic.

Any isocyanate functional group having a point of attachment carried bya methylene sensu stricto (—CH₂—) itself carried by an exocyclic andnontertiary sp³ carbon is regarded as linear.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chromatogram showing the distribution of the oligomers inExample 5.

FIG. 2 is a chromatogram showing the distribution of the oligomers inExample 6.

As regards the monomers and for the present description:

-   -   “aliphatic” is understood to mean any monomer, all the        isocyanate functional groups of which are aliphatic;    -   “aromatic” is understood to mean any monomer, all the isocyanate        functional groups of which are aromatic;    -   “mixed” is understood to mean any monomer, one functional group        at least of which is aliphatic and one functional group at least        of which is aromatic;    -   “cycloaliphatic” is understood to mean any monomer, all the        isocyanate functional groups of which are aliphatic and one at        least of which is cycloaliphatic;    -   “linear aliphatic” is understood to mean any monomer, all the        isocyanate functional groups of which are aliphatic, none of        which are cycloaliphatic and one at least of which is linear, or        which exhibits at least one polymethylene sequence, free in        rotation and thus exocyclic, (CH₂)_(π) where π represents an        integer at least equal to two.

To explain in a little more detail, the isocyanate monomers can be:

-   -   aliphatic, including cycloaliphatic and arylaliphatic (or        araliphatic), such as:        -   as linear (or simple) aliphatic, polymethylene diisocyanate            monomers which exhibit one or more exocyclic polymethylene            sequences (CH₂)_(π) where π represents an integer from 2 to            10, advantageously from 4 to 8, and in particular            hexamethylene diisocyanate, it being possible for one of the            methylenes to be substituted by a methyl or ethyl radical,            as is the case with MPDI (methylpentamethylene            diisocyanate);        -   as cyclic aliphatic (or cycloaliphatic): partially            “neopentylic” and cycloaliphatic; isophorone diisocyanate            (IPDI);        -   as cyclic aliphatic (cycloaliphatic) diisocyanate, those            derived from norbornane or the hydrogenated forms            (hydrogenation of the nucleus, resulting in a diaminated            ring subsequently subjected to isocyanation, for example by            phosgenation) of the aromatic isocyanates;        -   as araliphatic, arylenedialkylene diisocyanates (such as            OCN—CH₂-Φ-CH₂—NCO; a portion of which is regarded as linear            aliphatic, namely those having the isocyanate functional            group separated from the aromatic nuclei by at least two            carbons, such as (OCN—[CH₂]_(t)-Φ-[CH₂]_(u)—NCO) with t and            u greater than 1;    -   or also aromatic, such as toluoylene diisocyanate, mentioned        here as a matter of interest but the hydrogenated form of which,        on the other hand, is regarded as cycloaliphatic and is        advantageous, such as 1,3- and 1,4-BIC        (BisIsocyanatomethylCyclohexane).

Generally, the molecular weight of a monomer does not exceed 300 and isat least equal to 100.

According to the present invention, it is desirable for linear aliphaticmonomers to be used at least partially for the implementation of thepresent invention. To those which are mentioned above can also be addedlysine derivatives and in particular LDI (Lysine DiIsocyanate, resultingfrom ester of lysine) or LTI (Lysine TriIsocyanate, resulting from theester of lysine with ethanolamine), NTI (Nonyl TriIsocyanateOCN—(CH₂)₄—CH(CH₂—NCO)—(CH₂)₃—NCO) or UTI (Undecyl TriIsocyanateOCN—(CH₂)₅—CH(—NCO)—(CH₂)₅—NCO).

The majority of these monomers have a vapor pressure which is too highto meet regulatory requirements relating to safety at work.Consequently, these molecules are increased in size by polycondensingthem.

These condensations involve the isocyanate functional groups. As the“monomers” are polyfunctional with regard to isocyanate, thesecondensations can take place on two or more isocyanate functional groupsof the same molecule. It follows that these reactions can result inoligomers which are smaller or bigger in size depending on the degree ofconversion of the isocyanates.

The main polycondensates will be restated below:

The derivatives obtained by “trimerization”, that is to say that threeisocyanate functional groups belonging to three different molecules arecondensed to form an isocyanuric ring carrying three groups themselvescarrying an isocyanate functional group.

The main units, functional groups or rings liable to be formed on theoccasion of the trimerization may be restated:

Another way of increasing the size of the molecule is to condense themwith one another in the presence of water to form a derivative carryingthree isocyanate functional groups which is denoted under the expressionof biuret. The reaction below shows the reaction in the commonest case,that is to say the case where the three molecules to be condensed arethe same:

It is also possible to condense these monomers with alcohols, inparticular polyols, which gives carbamate and then allophanatepolyfunctional compounds.

In the polyisocyanate compositions, in addition to the predominantpolycondensates, more often than not minor amounts of variouscondensation types are encountered.

The great majority of isocyanates were until recently essentiallydissolved in organic solvents. The use of organic solvents isincreasingly often subject to criticism by the authorities in charge ofsafety at work as these solvents, or at least some of them, are supposedto be toxic or chronically toxic. This is the reason why attempts areincreasingly being made to develop technologies which comprise only avery small amount of solvent, indeed which are even devoid of solvent.

In particular, in order to reduce the use of organic solvent, thepresence of which is supposed to be toxic to those who handle it andharmful to the environment, the proposal has been made to developisocyanate compositions which are less viscous. This lowering inviscosity makes it possible to reduce the amount of solvent and rendersthe compositions more capable of being emulsified.

Furthermore, the market is demanding a compound which makes it possibleto carry out a twofold crosslinking and thus to produce a twofold ormultiple functionality.

In addition, a search is always underway for compositions which makepossible strong adhesion, with or without primer, or which are evencapable of acting as primer.

A search is thus underway for an adhesion promoter.

Mention may in particular be made, among the most widely used oligomericpolyisocyanate compositions, of the oligomer mixture exhibiting a biuretunit and familiarly denoted by “biuret”.

This biuret is currently produced by the action of water on isocyanatemonomers in the presence of a very small amount of acid.

The degree of conversion of the monomer is of the order of 45%.

In the case where the monomer is hexamethylene diisocyanate, theviscosity of the product resulting from the synthesis after distillationof the monomer is of the order of 9000 mPa·s.

There are two significant disadvantages to this synthesis: the formationof insoluble ureides, which it is advisable to remove, and, on the otherhand, the relatively high viscosity of the product after distillation ofthe monomer.

Generally, ureas often exhibit problems of insolubility, in particularwith regard to compounds with a markedly lipophilic nature.

Furthermore, the market requires compositions exhibiting a highfunctionality.

Furthermore, a few isocyanate monomers comprising an alkoxysilanefunctional group are known. Mention may be made, by way of examples, ofisocyanatopropyltrimethoxysilane and isocyanatopropyltriethoxysilane.These volatile monomers are classified as toxic.

Polyisocyanates comprising alkoxysilane functional groups are regardedas difficult to access, in particular when a high content ofalkoxysilane groups is desired. They are generally obtained by graftingalkoxysilane molecules comprising a mobile hydrogen functional group tothe isocyanate functional groups of a polyisocyanate. Generally, thealkoxysilane molecules used are amines which, by reaction with theisocyanate functional groups of a polyisocyanate, give alkoxysilanepolyureas which are generally solid and not very soluble in organicsolvents. These compounds do not give homogeneous mixtures.

This low solubility in organic solvents has led users to graft only aportion of the isocyanate functional groups and to obtain alkoxysilaneurea isocyanate hybrid compounds.

However, this partial grafting solution is not always advantageous asthe control of the grafting is not easy and depends on the structures ofthe polyisocyanates used, and in particular nonspontaneouscrystallization phenomena occur, resulting in crystallization of thealkoxysilane urea polyisocyanates during the storage of formulationscomprising these derivatives.

Furthermore, these alkoxysilane urea structures bring about increases inthe viscosity of the formulations and thus require larger volumes ofsolvent in order to be able to be applied correctly. This increase insolvents is not or not very compatible with the step of reducingvolatile organic discharges to the atmosphere.

This is why one of the aims of the present invention is to provide aprocess which reduces or eliminates the formation of insoluble ureides.

Another aim of the present invention is to provide a technology whichmakes it possible to render compatible isocyanate and silane and inparticular alkoxysilanes.

Another aim of the present invention is to provide isocyanatecompositions in which the isocyanate comprises a biuret group.

Another aim of the present invention is to provide a process which makesit possible to reduce the viscosity of the final composition for thesame degree of conversion of the monomer(s), the measurement of theviscosity being carried out under “standard” conditions, after removalof the residual monomer(s) (the compositions targeted exhibit, byweight, at most 1%, advantageously at most 0.5%, preferably at most0.2%, more preferably at most 0.1%). For the measurement of theviscosity, see Standard NFT 30-029 (October 1980).

Another aim of the present invention is to provide compositionscomprising a biuret group which exhibit a reduced viscosity.

Another aim of the present invention is to provide polyisocyanatecompositions of high functionality which can be used alone or as amixture with others.

Another aim of the present invention is to provide polyisocyanatecompositions having a twofold or multiple functionality which makes itpossible to carry out a twofold crosslinking.

Another aim of the present invention is to provide polyisocyanatecompositions a strong adhesion, with or without primer, or which areeven capable of acting as primer.

These aims and others which will become apparent subsequently areachieved by means of a composition comprising at least two distinctoligomeric compounds comprising at least three units and at most 5 (tolimit perhaps at 4) units chosen from aminoalkylsilane units and diaminounits and at least one functional group chosen from isocyanatefunctional groups and from those which derive therefrom, characterizedin that one of said compounds comprises at least two aminoalkylsilaneunits and in that another comprises at least two diamino units.

Advantageously, these compositions do not comprise monomer; see abovewith regard to the measurement of the viscosity.

In said composition, it is desirable for there to be as little true ureafunctional group as possible; advantageously, the ratio of the true ureafunctional groups (numerator) to the acylurea and biuret functionalgroups (denominator) is at most equal to 1/2, advantageously to 1/3,preferably to 1/5, more preferably to 1/10. Such ratios are readilyaccessible by spectroscopic measurements.

When there is no biuret or acylurea, the content of true urea functionalgroup is advantageously at most equal to 1% of the isocyanate (NCO)functional groups, preferably to 0.5%.

The following unit is regarded as true urea functional group:

—NH—CO—N<, in which the bonds of the nitrogens left open are connectedonly to hydrogen and/or to an aliphatic radical.

It is desirable, with regard to the combined composition, for the ratioin equivalents of the aminoalkylsilane units to the diamino units to beat least equal to 15%.

Generally, said oligomeric compounds each represent at least 3%,advantageously at least 5%, preferably at least 8%, by weight of thecomposition.

Furthermore, it is desirable for said oligomeric compounds to represent,for each category, at most 2/3, advantageously, preferably 1/3, byweight of the composition.

According to a preferred implementation of the present inventioncomposition as claimed in claims 1 to 4, characterized in that, withregard to the combined oligomeric compounds (that is to say, oligomericcompounds comprising at least three units and at most 5 units chosenfrom aminoalkylsilane units and diamino units and at least onefunctional group chosen from isocyanate functional groups and from thosewhich derive therefrom), the compounds in which the aminoalkylsilaneunits represent at least two fifths of the units under consideration(aminoalkylsilane units and diamino units) form at least 1/5 of themixture.

said functional groups which derive from the isocyanate functionalgroups are advantageously chosen from the carbamate, uretidinedione,isocyanurate, biuret, allophanate, pseudoallophanate,4,6-dioxo-2-iminohexahydro-1,3,5-triazine, iminooxadiazinedione and2-imino-4-oxo-1,3-diazetidine functional groups.

composition as claimed in claims 1 to 6, characterized in that saidaminoalkylsilane unit corresponds to the formula (I):

where Ξ represents either a single bond or a chalcogen, preferably anoxygen.

Advantageously, said compounds are compounds comprising a biuretfunctional group.

Advantageously, the composition exhibits a content of biuret functionalgroup (>N—CO—N(−)—CO—N<, MW=84) at least equal to 5%, advantageously to8%, preferably to 10%. This content of biuret functional group(>N—CO—N(−)—CO—N<, MW=84) is at most equal to 20%, advantageously to18%, preferably to 16%.

The composition exhibits a total content of isocyanate functional group(free and blocked) at least equal to 5%, advantageously to 8%,preferably to 10%, more preferably to 12%.

According to one implementation of the present invention, thecomposition exhibits a content of free isocyanate functional group atleast equal to 5%, advantageously to 8%, preferably to 10%, morepreferably to 12%.

According to one implementation of the present invention, thecomposition exhibits a content of blocked isocyanate functional group atleast equal to 5%, advantageously to 8%, preferably to 10%, morepreferably to 12%.

According to the present invention, the composition (with unblockedisocyanate functional groups) can exhibit a viscosity at most equal to6000 mPa·s, advantageously to 4000 mPa·s, preferably to 3000 mPa·s,which is remarkable for biuret-based polyisocyanate compositions.

The composition comprises at most 2%, advantageously at most 1%,preferably at most 0.5%, by weight of isocyanate monomer(s) (generallydiisocyanatoalkane).

Furthermore, according to an advantageous embodiment of the invention,the composition can comprise at most 2%, advantageously at most 1%,preferably at most 0.5%, by weight of isocyanatoalkylsilane(corresponding to the aminoalkylsilane).

Another aim of the present invention is to provide a process for thepreparation of an isocyanate composition comprising biuret functionalgroups, characterized in that at least one isocyanate monomer is broughtinto contact with an aminoalkylsilane (or silanoalkylamine) so that anisocyanatoalkylsilane is formed.

The process is based on the result of the study of the equilibria setout below. This process makes it possible to prepare biuret without theaddition of water and while producing, as potential by-product, anisocyanatosilyl derivative (isocyanatoalkoxysilane) which is difficultto manufacture (see above), in particular of formula Ib

The reaction with the amine begins as follows:

where R represents an amine-carrying radical and in particular

where R′ represents the residue of an isocyanate after ignoring oneisocyanate functional group.

However, the reversible formation of the biuret can result in theformation of the isocyanate on the radical of the amine if the reactionmixture is heated sufficiently for a long enough period of time:

This reaction, which is promoted by the relative volatility of the silylradical, makes it possible to obtain all the alternative forms of thebiuret, if the reaction is carried out at reflux, or the isocyanateinstead of the starting amine functional group, if the R—NCO formed isdistilled off.

This equilibrating of the composition via the exchange with the freemonomers results in the formation (with respect to the combined biuretfunctional groups) of at least 5%, advantageously 7%, preferably 10%, ofbiuret functional groups which do not carry a silanoalkyl chain. Thisstabilizes the composition, rendering it more homogeneous.

In order for this equilibrating to take place under satisfactoryconditions, it is desirable for the ratio, expressed in equivalents, ofthe isocyanate functional groups to the number of hydrogens carried bythe amine functional groups to be at least 4, advantageously at least 6,preferably at least eight.

It is also desirable to be positioned at a high temperature of at least140° C., advantageously 150° C., preferably at 160° C., and/or to usebiuretization catalysts, such as strong and/or moderate acids.

More specifically, the present invention comprises the preparation ofpolyisocyanate compositions, the polyisocyanates comprising acyl orcarbamoyl urea units and comprising at least one (R₃—X)_(3-m)Si(R₂)_(m)—unit, obtained according to a process which employs a compoundcomprising at least one isocyanate functional group, preferably at leasttwo isocyanate functional groups, with a compound comprising at leastone primary or secondary amine functional group and/or optionally acompound comprising at least one carboxylic acid functional group. Theprocess is characterized by a single-stage reaction with an excess ofisocyanate compounds with respect to the amine introduced at atemperature of between 100 and 200° C., preferably between 110° C. and180° C. The reaction time is between 1 and 10 hours and the excessmonomer is subsequently removed by thin film distillation so that thefinal product comprises a content of HDI monomer of less than 2%,preferably less than 1%.

The degree of conversion of isocyanate is generally set by the amount ofamines introduced.

The content of oligomers in the compositions varies with the ratio ofisocyanate functional groups to amine functional groups.

Generally, the structures which are subject matters of the inventiongive relatively low viscosities due to the formation of intramolecularhydrogen bonds in the biuret and/or acylurea units.

Generally, the biuret compositions comprise the structures which can berepresented schematically by the following general formula;A-(NCO)_(z)—(Si(R₂)_(m)(X—R₃)_(n))_(y)withA representing the residue of a backbone comprising biuret and/oracylurea structures;z representing a number between 0 and 30;y representing a number between 1 and 30;m representing an integer within the closed range (that is to saycomprising the limits) 0 to 3, advantageously at least equal to 2,preferably to 3;n representing an integer within the closed range (that is to saycomprising the limits) 0 to 3, advantageously at most equal to 2;with the condition that m+n=3;R₂ representing a linear or branched hydrocarbon chain of 1 to 20 carbonatoms, preferably of 1 to 12 carbon atoms, it being possible for thishydrocarbon chain to be aliphatic, including aralkyl, or aromatic,optionally interrupted by heteroatoms, it being possible for the R₂chain to be of alkylene type if the two terminal carbons of this chainare bonded to the silicon;R₃ representing a linear or branched hydrocarbon chain of 1 to 20 carbonatoms, preferably of 1 to 12 carbon atoms, it being possible for thishydrocarbon chain to be aliphatic or aromatic or aralkyl, optionallyinterrupted by heteroatoms, it being possible for the R₃ chain to be ofalkylene type if the two terminal carbons of this chain are bonded totwo groups X carried by the same silicon atom;X═O or S.

Mention may be made, as nonlimiting examples of the general structure,of the following structures:

-   -   structures comprising biuret units, hereinafter recorded from 1        to 5    -   acylurea structures, recorded from 6 to 10

Structure 1: “True” biuret comprising two isocyanate units and onealkoxysilane unit, the amine functional group inserted in the biuretcarrying a group Y which can be hydrogen or a linear or branchedhydrocarbon chain of 1 to 20 carbon atoms which is aliphatic, includingaraliphatic, or aromatic, optionally interrupted by heteroatoms.

with Y representing a hydrogen or a hydrocarbon chain and

a hydrogen bond

Structure 2: “True” biuret comprising two isocyanate units and onealkoxysilane unit, the amine functional group inserted in the biuretcarrying a group Y which can only be hydrogen.

Polybiuret structures comprising 2 NCO functionalities: products of theoligomerization of the structures 1 and/or 2 to result in oligomericsequences comprising from 2 to 20 units. These sequences can berepresented schematically as follows, the distribution of the structuresbeing random along the chain.

with Y representing a hydrogen or a hydrocarbon chain,

representing a hydrogen bond and with “a” and “b” representing a valueranging from 2 to 20

The compositions also comprise biuret structures comprising anisocyanate unit and two alkoxysilane units (structure 3) and muchsmaller amounts of biuret structures composed of 3 alkoxysilane units(structure 4). The latter structures are only present under certainconditions.

Structure 3 can also be incorporated in polybiuret sequences presentedabove and, in this case, constitute chain-limiting agents (blocking ofthe terminal ends of chains) due to their isocyanate monovalency.

The presence of these structures 3 and 4 is explained by the conditionsof the process involved and is based on a transisocyanation reactionwhich can be accelerated by the temperature and by the catalystselected.

Structure 3: Biuret comprising two alkoxysilane functional groups andone isocyanate unit.

Structure 4: Biuret comprising three alkoxysilane functional groups

The composition also comprises sequences with a functionality of greaterthan 2, even if a diisocyanate is used alone in the reaction with amonoaminoalkylsilane. These sequences are the consequence of the processinvolved.

Structure 5 represents an example of polybiuret sequences with afunctionality of greater than 2.

Structure 5: example of polybiuret sequence with a functionality ofgreater than 2

with

-   -   R the residue of an isocyanate or polyisocyanate molecule        carrying at least one isocyanate functional group,

R₁ the residue of a molecule carrying at least one silane functionalgroup, generally a linear or branched hydrocarbon chain of 2 to 20carbon atoms, preferably of 3 to 12 carbon atoms, it being possible forthis hydrocarbon chain to be aliphatic or aromatic or aralkyl,optionally interrupted by heteroatoms,

-   -   R₂ and R₃, which are identical or different, defined as above,    -   n between 1 and 3 and n+m=3,    -   X═O or S.

Structures Comprising Acylurea Units:

The structures comprising acylurea units can be written as for thebiuret structures, except that the R₄—C(═O)— unit replaces theR—NH—C(═O)— unit in the biuret structures.

The following acylurea structures 7 to 10 are presented by way ofexamples. The polyacylurea sequences are not represented but areanalogous to the polybiuret sequences.

Acylurea Structures 7 to 9

with

-   -   R₄ representing the residue of a molecule carrying at least one        carboxyl functional group which has reacted to give the        N-acylurea functional group.

In the case of a diacid (R₄—(COOH)₂), the acylurea structure thenbecomes

Structure 10: example of bisacylurea structure comprising alkoxysilaneunits

Aside from these structures 1 to 10, the compositions also compriseoligomeric or polymeric molecules comprising sequences comprising theunits described above.

The compositions can also comprise structures comprising the followingunits:

Allophanate: —R—N[—C(═O)—NH—R—NCO]—C(═O)—O—R₅

Carbamate: —R—NH—C(═O)—O—R₅

Urea: —R—NH—C(═O)—NH—R₆— or —R—NH—C(═O)—N—(R₆)(R₇)

Uretidinedione:

Isocyanurate:

Oxadiazinetrione:

Iminotrimer:

The synthesis of these products comprises the reaction of a compoundcomprising at least one isocyanate functional group, preferably at leasttwo isocyanate functional groups, with a compound comprising at leastone primary and/or secondary amine functional group and at least onealkoxydialkylsilane functional group and/or one alkyldialkoxysilanefunctional group and/or one trialkoxysilane functional group in thepresence optionally of a compound comprising at least one carboxylicacid functional group and of a catalyst. The reaction can be carried outin the presence or in the absence of solvent.

The isocyanate compounds used comprise at least two and at most 10isocyanate functional groups and preferably at most 4. They can bealiphatic or cycloaliphatic.

Mixtures of polyisocyanate compounds can also be used. In the case ofpolyisocyanate mixtures, compounds comprising only a single isocyanatefunctional group per mole of compound can be incorporated but theircontent of isocyanate functional groups then does not exceed 50 mol %,preferably 25 mol %, of the isocyanate functional groups of the mixture.Polyisocyanate compounds comprising more than 3 isocyanate functionalgroups and less than 25 can also be incorporated in the mixture buttheir content of isocyanate functional groups does not exceed 50 mol %of the isocyanate functional groups of the mixture and preferably doesnot exceed 25 mol %.

Mention may be made, as nonlimiting examples of aliphatic isocyanatecompounds, of diisocyanates, such as hexamethylene diisocyanate (HDI),2-methylpentane diisocyanate (MPDI), dodecane diisocyanate (DDI), or themethyl or ethyl ester or esters of heavier alcohols of lysinediisocyanate (LDI), or triisocyanates, such as the isocyanatoethyl esterof lysine diisocyanate (LTI) or 4-isocyanatomethyl-1,8-octamethylenediisocyanate (TTI).

Mention may be made, as nonlimiting examples of cycloaliphaticisocyanate compounds, of diisocyanates, such as norbornane diisocyanate(NBDI), bis(isocyanatomethyl)cyclohexane (BIC) or isophoronediisocyanate (IPDI).

Mention may be made, as nonlimiting examples of monoisocyanatecompounds, of butyl isocyanate, isocyanatopropyltrialkoxysilane oroctadecyl isocyanate.

Mention may be made, as nonlimiting examples of polyisocyanatecompounds, of the isocyanurate oligomers of HDI or of IPDI.

The compounds carrying at least one primary and/or secondary aminefunctional group used for the reaction have the following structures:Y—NH—R₅—Si(R₃—X)_(3-m)(R₂)_(m) orY—NH—R₆—N(—Y)—R₅—Si(R₃—X)_(3-m)(R₂)_(m) orR₆—[(NH—R₅—Si(R₃—X)_(3-m)(R₂)_(m))]_(z)with

-   -   Y═H or a linear or branched hydrocarbon chain of 1 to 20 carbon        atoms which is aliphatic or aromatic or araliphatic and which is        optionally interrupted by heteroatoms,    -   R₅ a linear or branched hydrocarbon chain of 1 to 20 carbon        atoms which is aliphatic or aromatic or araliphatic and which is        optionally interrupted by heteroatoms; R₅ is preferably an        aliphatic hydrocarbon chain of 1 to 8 carbon atoms,    -   R₆ a linear or branched hydrocarbon alkylene chain of 1 to 20        carbon atoms which is aliphatic or aromatic or araliphatic and        which is optionally interrupted by heteroatoms,    -   z=2 to 6, preferably z=2.

In the specific case of the preparation of acylureas, it is possible touse all or part of the compounds carrying at least one primary and/orsecondary amine functional group and at least one silane functionalgroup in the form of a salt of the compound carrying at least onecarboxylic acid functional group.

The compounds carrying at least one carboxylic acid functional group arealiphatic or aromatic or heterocyclic compounds. They comprise at leastone carboxylic acid functional group, at most 6, preferably at most 2.The carbon number is between 2 and 20, preferably between 2 and 12.

Mention may be made,

as nonlimiting examples of compounds comprising at least one carboxylfunctional group, of acetic acid, propionic acid, isobutyric acid,pivalic acid, benzoic acid, 2-ethylhexanoic acid, undecanoic acid,stearic acid and their branched homologs,

as nonlimiting examples of compounds comprising at least two carboxylfunctional groups, of adipic acid, dodecanedioic acid, undecanedioicacid, glutaric acid and their branched homologs.

The process for the synthesis of the polybiurets comprises:

-   -   introducing an isocyanate, preferably a diisocyanate, or a        mixture of isocyanates into a reactor,    -   optionally adding a biuretization catalyst, such as a carboxylic        acid or a Lewis acid, such as dibutyltin dilaurate,    -   heating this mixture of 110° C.,    -   adding, to this mixture, a compound carrying at least one        primary or secondary amine functional group and carrying a        silane functional group, or a mixture of these amines,    -   maintaining the reaction medium at a temperature of between 100        and 200° C., preferably between 110° C. and 160° C., for a time        of between 1 and 5 hours,    -   removing the unreacted monomer by a suitable process, such as        vacuum distillation on a thin film device,    -   recovering the polybiuret product comprising alkoxysilane units        and comprising isocyanate units.

An alternative form of the process comprises adding the amine to theisocyanate under cold conditions and subsequently heating to atemperature of between 100 and 200° C., preferably between 110 and 160°C., for a time of between 1 and 5 hours.

Another alternative form of the process comprises adding the isocyanateto the amine or to the mixture of amines comprising silane functionalgroups and raising the reaction temperature until reaction is obtainedat a temperature of between 100 and 200° C., preferably between 110 and160° C., for a time of between 1 and 5 hours.

The isocyanate functional groups/amine functional groups ratio isbetween 2 and 50, preferably between 4 and 25.

Another alternative form of the process for the synthesis of polybiuretscomprises reacting a compound comprising at least one isocyanatefunctional group with a compound carrying at least onealkoxydialkylsilane functional group and/or one alkyldialkoxysilanefunctional group and/or one trialkoxysilane functional group and atleast one urea or thiourea functional group. The reaction medium ismaintained at a temperature of between 100 and 200° C., preferablybetween 110 and 160° C., for a time of between 1 and 5 hours, in theoptional presence of a catalyst chosen from carboxylic acids and/orLewis acids.

The structures obtained can be written as follows:

The compounds carrying at least one alkoxydialkylsilane functional groupand/or one alkyldialkoxysilane functional group and/or onetrialkoxysilane functional group and at least one urea functional grouphave the formulae:(Y)₂—N—C(═Z)—N(—Y)—R₅—Si(R₃—X)_(3-m)(R₂)_(m) orC(═Z)—[(NY—R₅—Si(R₃—X)_(3-m)(R₂)_(m))]₂with Y as defined above and at least one of the Y groups is equal to H,it being possible for Y to be an optionally substituted alkylene chainbridging the two nitrogens of the urea,A-N(Y)_(d)—C(═Z)—N(Y)—R₅—Si(R₃—X)_(3-m)(R₂)_(m)withA representing the residue of a hydrocarbon backbone comprising at leastone primary or secondary amine functional group inserted in a urea orthiourea bond,with Y as defined above and at least one of the Y groups is equal to H,it being possible for Y to be an optionally substituted alkylene chainbridging the two nitrogens of the urea,Z═O or S.

Mention may be made, as nonlimiting examples of ureas, of aminocarbonylamino 1 propyltrimethoxysilane, amino carbonyl amino 1 propyltriethoxysilane, N2(propyl trimethoxysilane) imidazolidin 1 one orN2(propyl triethoxysilane) imidazolidin 1 one.

The process for the synthesis of the polyacylurea biurets comprises

-   -   adding, to the starting isocyanate or to the starting        polyisocyanate mixture, a compound carrying at least one        carboxylic acid functional group,    -   raising the temperature to a value of approximately 100° C.,        plus or minus 20° C.,    -   adding, to this reaction medium, a compound carrying at least        one primary or secondary amine functional group and carrying at        least one silane functional group, or a mixture of these amines,    -   maintaining the reaction medium at a temperature of between 100        and 200° C., preferably between 110° C. and 160° C., for a time        of between 1 and 5 hours,    -   removing the unreacted monomer by a suitable process, such as        vacuum distillation on a thin film device,    -   recovering the polyacylurea biuret product comprising        alkoxysilane units and comprising isocyanate units.

An alternative form of the process comprises adding the amine to theisocyanate and to the acid compound under cold conditions andsubsequently heating to a temperature of between 100 and 200° C.,preferably between 110° C. and 160° C., for a time of between 1 and 5hours.

Another alternative form of the process comprises adding the isocyanateto the amine or to the amine carboxylate or mixture of amines comprisingsilane functional groups and raising the reaction temperature untilreaction is obtained at a temperature of between 100 and 200° C.,preferably between 110 and 160° C., for a time of between 1 and 5 hours.

The ratio of carboxyl functional groups to isocyanate functional groupsat the start is between 1/20 and 1/4.

Generally, the NCO/nucleophiles (COOH+amines) ratio is between 1 and 50,preferably between 2 and 25.

The degree of conversion of the isocyanate monomers depends on theNCO/amines and NCO/COOH ratio. The greater the NCO/nucleophiles ratio,the lower the degree of conversion of isocyanate functional groups.

Surprisingly, in comparison with conventional biurets obtained fromhexamethylene diisocyanate (HDI) and for comparable degrees ofconversion of isocyanate functional groups, the compounds which aresubject matter of the invention are characterized by a lower viscosity,which is an advantageous component in reducing the volatile organiccompounds discharged to the atmosphere. Thus, some biurets obtained fromHDI and 1 aminopropyltriethoxysilane exhibit a viscosity of 2570 mPa·sat 25° C. for a degree of conversion of the order of 45%, whereas HDIbiurets result in viscosities of the order of 9000 mPa·s at 25° C. forcomparable degrees of conversion.

The viscosity of the compounds which are subject matters of theinvention very clearly depends on the isocyanate monomer used, aliphaticcompounds giving generally higher viscosities than short-chain (4 to 10chain members) aliphatic isocyanate derivatives.

The compounds of the invention obtained by the process are characterizedby:

-   -   the presence of at least one biuret and/or acylurea bond,    -   and an NCO content of between 0 and 20% by weight of NCO per 100        g of solution, preferably of between 1 and 19%,    -   and a content of Si—X—R₃ units, expressed as % by weight of        silicon (Si), of between 0.1% and 17.5%, preferably of between        0.5% and 13%, and an oligomeric distribution.

The compounds of the invention exhibit a twofold reactivity, thereactivity of the isocyanate functional groups and the reactivity of thealkoxysilane functional groups.

The compounds of the invention can thus exhibit very broad ranges offunctionality according to the compounds involved and according to theNCO/nucleophiles (amine, urea, amides) ratio involved.

Thus, aminoalkyltrialkoxysilanes, monomeric compounds possessing threepotentially reactive alkoxysilane functional groups (functionality 3),rapidly result in compounds having a high functionality. Thus, truebiuret compounds of structure 1 and 2 exhibit a potential functionalityof 5 (two isocyanate functional groups and three alkoxysilane functionalgroups).

The tris biuret comprising three biuret units will have a functionalityof 11 (two isocyanate functional groups and 3×3 alkoxysilane functionalgroups).

It is thus difficult to calculate the mean functionality of thecrosslinking composition insofar as each alkoxysilane group constitutesa potential site of reaction.

The compositions are characterized by a distribution composed of atleast one of the following compounds:

-   -   mixed true biuret and/or mixed true acylurea compounds of the        invention comprising at least one silane functional group devoid        of free isocyanate functional group,    -   and/or mixed true biuret and/or mixed true acylurea compounds of        the invention comprising at least one silane functional group        and at least one free isocyanate functional group,    -   and/or polybiuret and/or acylurea compounds of the invention        comprising at least one silane functional group devoid of free        isocyanate functional group,    -   and/or true polybiuret and/or true polyacylurea compounds of the        invention comprising at least one silane functional group and at        least one free isocyanate functional group.

Optionally, the composition comprises isocyanates or polyisocyanates notcomprising silane units, namely:

-   -   starting mixture of isocyanates or isocyanate and alkyl        carbamate compounds,    -   and optionally starting mixture of isocyanates or isocyanate and        alkyl allophanate compounds,    -   isocyanate isocyanurate compounds,    -   biuret compounds.

The term “true biuret” is understood to mean the reaction product of twoisocyanate functional groups with an amine functional group. The term“mixed true biuret” is understood to mean the preceding compound, thebackbone of which carrying the amine functional group is different fromthe backbone of which carrying the isocyanate functional groups.

The compounds which are subject matters of the invention can be used forthe synthesis of functional derivatives or the preparation ofcompositions for mastics or for coatings applied to organic or inorganicsurfaces (metal, plastics, wood, cloth, leather, concrete, and the like)for decorative, functional and/or protective purposes, as couplingagents between a surface and a functional organic or inorganic compound.

The compounds of the present invention can also be incorporated in themanufacture of materials based on polyurethanes (foams), on elastomers,on fibers or on rubber.

The fields of application are thus very diverse (paints, varnishes,adhesives, tires, and the like) and relate just as well to interiorapplications as to exterior applications (exposed to natural light) orapplications exposed to specific media (materials immersed in water, andthe like).

These compounds can also be used to modify the surface properties ofcoatings (hydrophobization, hardness, and the like).

The compounds of the invention exhibit low coloring indices of less than200 Hazen.

The isocyanate functional groups carried by the compounds of theinvention of the final mixture can be definitively or temporarily andcompletely or partially functionalized by various nucleophiliccomponents which can be chosen from:

-   -   alkoxysilanes comprising nucleophilic functional groups, such        as, for example, amino- or thioalkyltrialkoxysilanes,    -   hydroxyalkyl acrylates,    -   chain extenders, such as diamines, diols or polyols,    -   agents for temporarily blocking the isocyanate functional groups        which are well known to a person skilled in the art, such as        oximes, pyrazoles, triazoles, imidazoles, lactams or ketoesters,        it being possible for all these compounds to carry one or more        substituents. Mention may thus be made, as nonlimiting examples,        of methyl ethyl ketoxime, 3,5-dimethylpyrazole, ε-caprolactam,        and the like.

Some of these derivatives constitute compounds possessing a twofoldreactivity. Thus, mention may be made, as nonlimiting examples, of thecompounds of the invention in which the isocyanate functional groups areblocked by a thermolabile temporary blocking agent and the compounds ofthe invention in which the isocyanate functional groups arefunctionalized by acrylate or methacrylate derivatives.

The compositions which are a subject matter of the invention can be used

-   -   to react with the hydroxyl functional groups of polyol polymers,        such as cellulose, guars or wood, in order to confer various        properties, such as water repellency, thereon,    -   to react with functional groups comprising a mobile hydrogen of        polyols, such as the hydroxyl functional groups of a polyol        polymer and/or the amine or thiol or carboxyl functional groups        of polymers, in order to obtain polyurethane and/or polyurea        and/or polythiourethane and/or polyamide coatings,    -   as additives for coating, varnish or adhesive formulations, in        order to contribute particular properties, such as, for example,        the lowering of surface tension,    -   to react with hydroxyl or silanol functional groups of inorganic        compounds, such as silica or titanium dioxide or zirconia,    -   to react with other silane compounds carrying at least one        alkoxysilane functional group, such as        epoxyalkyltrialkoxysilanes, alkyltrialkoxysilanes,        tetraalkoxysilanes, and the like.

These compounds can be reacted in the organic phase or in the aqueousphase.

In the case of coatings of polyurethane or polyurea type, the coproductsof reaction with the compounds of the invention can be:

-   -   acrylic poly(thi)ols derived from the polymerization of        monomeric compounds carrying activated double bonds, such as        (cyclo)alkyl or hydroxyalkyl acrylates or methacrylates,    -   acrylic polyamines,    -   polyester polyamine or poly(thi)ol polymers resulting from the        polycondensation of a diacid or diester or carbonate with a diol        or an aminoalcohol,    -   polycarbonate poly(thi)ol polymers,    -   polysiloxane compounds comprising alkyl units carrying hydroxyl        and/or amino and/or thio functional groups polyamines,    -   polyethers carrying hydroxyl and/or amine and/or thiol        functional groups hydroxyl functional groups,    -   polyprene compounds comprising hydroxyl or carboxylic acid        functional groups,    -   alkoxysilanes,    -   or polymeric compounds comprising temporarily blocked hydroxyl,        thiol or amine functional groups. Mention may be made, as        examples of these blocked functional groups, of imines,        dioxolanes, acetals, and the like.

The synthesis of these polymers and the constituent monomers of thesepolymers are widely known to a person skilled in the art. Mention may bemade, as examples of monomers carrying double bonds, of n-butyl,cyclohexyl, methyl, isopropyl or tert-butyl acrylates and methacrylates,acrylamide and methacrylamide as well as their N-alkylated derivatives,acrylic acid and methacrylic acid, styrene, butadiene or vinylderivatives.

Mention may be made, as nonlimiting examples of monomers of thepolycondensation reaction, of adipic acid, succinic acid, glutaric acid,dodecanedioic acid, phthalic acid, esters of these diacids, alkylenecarbonates, such as methylcarbonate, ethylcarbonate, propylenecarbonateor ethylenecarbonate, or diols, such as butanediols, hexanediols,cyclohexanediols, and the like.

Mention may be made, as examples of polyether compounds or epoxypolymers, of ethylene oxide or propylene oxide.

Compounds such as various fillers, catalysts, rheology additives orpigments can be added to the formulations in order to introduce thedesired properties.

The following examples are representative of the invention.

Analytical Methods and Definitions:

A compound comprising a mobile hydrogen, the addition compound of whichwith a linear aliphatic isocyanate functional group exhibits a releasetemperature at most equal to 180° C., is regarded as a blocking agent.

Test with Octanol—Definitions

“Release” (or This is the lowest temperature at which the “unblocking”)blocking agent of the blocked isocyanate is temperature: displaced to alevel of 9/10 (mathematically rounded) by a primary monoalcohol (theprimary alcohol is generally octanol). Lifetime on storage: To ensure agood lifetime on storage, it is preferable to choose blocked isocyanatefunctional groups for which the test with octanol shows a “release” at80° C., advantageously at 90° C., at most equal to 90%. Progress of thereaction: The reaction is regarded as complete if it is carried out tomore than 90%.

Procedure

Approximately 5 mmol as protected blocked NCO equivalent to be evaluatedare charged to a tube of Schott type with magnetic stirring.

2.5 to 3 ml of 1,2-dichlorobenzene (solvent) and the equivalent of1-octanol (5 mmol, i.e. 0.61 g and optionally with the catalyst to betested with the blocking group) are added.

The reaction medium is subsequently brought to the test temperature.Heating is then carried out at the test temperature for 6 h, so as todeblock and thus render reactive the isocyanate functional groups. Oncompletion of the reaction, the solvent is removed by vacuumdistillation and the residue is analyzed by NMR, mass and infraredspectroscopy.

From these data, the percentage of blocked isocyanate functional groupcondensed with the 1-octanol is evaluated.

Quantitative Determination of the Isocyanate Functional Groups:

The standardized method for the quantitative determination of isocyanatefunctional groups by the “dibutylamine” method is used. Back titrationby a standard HCl solution of the N,N-dibutylamine not consumed by thereaction with the isocyanate functional groups of the mixture to bequantitatively determined. The difference between the N,N-dibutylaminewhich is reacted and the amount introduced makes it possible to measurethe content of isocyanate functional groups of the mixture to bequantitatively determined.

Determination of the Mn and Mw Values of the Polymers:

Gel permeation chromatography is used as method for determining thenumber-average and weight-average molecular weights. Polystyrenestandards of known molecular weight are used to calibrate the gelpermeation columns. The elution solvent used is a good solvent for thestandard polymers and for the polymers to be analyzed. It is chosentaking into account the constraints introduced by the method for thedetection of the polymers (refractometry or analysis by ultravioletabsorption or analysis by infrared). This solvent is chosen from ethers,such as tetrahydrofuran, chlorinated derivatives, such asdichloromethane, and the like.

The elution volume of the polymers to be analyzed is compared with theelution volumes of the standard polymers and the molecular weight isthus deduced therefrom. The constituent oligomers eluted of the mixtureto be analyzed can also be recovered separately for analysis andcharacterization by various structural analytical techniques, such as ¹HNMR, ¹³C NMR, infrared, and the like.

ABBREVIATIONS USED

HDI: hexamethylene diisocyanate

GPC: gel permeation chromatography

DBA: N,N-dibutylamine

APTEO: aminopropyltriethoxysilane

APTMO: aminopropyltrimethoxysilane

SYNTHETIC EXAMPLES Example 1 Biuret of Hexamethylene Diisocyanate (HDI)and of Aminopropyltriethoxysilane (APTEO) (CMI 1487)

1680 g of hexamethylene diisocyanate are introduced into a 3 l reactorequipped with a mechanical stirrer, dropping funnels and a refluxcondenser and rendered inert with nitrogen. The starting NCO content is1.19. The temperature of the reaction medium is 18.5° C. 456.5 g ofaminopropyltriethoxysilane (APTEO) are then added over one hour. TheNCO/amine molar ratio is 10/1. An exothermal drift and the appearance ofa white precipitate in the reaction medium are observed. The exothermicreaction is taken advantage of in raising the temperature of thereaction medium to 100° C. The temperature of the reaction medium thusgradually rises: at the end of 10 minutes after the addition, thetemperature of the reaction medium is 25° C., 43° C. after 30 minutesand 93° C. after 55 minutes. At the end of one hour, the precipitateobserved is virtually entirely soluble in the reaction medium. From theend of the addition, the temperature of the reaction medium is raised to140° C. by contributing external energy. After reacting for two hours at140° C., the content of isocyanate functional groups of the reactionmedium is 0.729 mol of NCO per 100 g of reaction medium.

The reaction medium is then purified by 2 successive distillations ofthe HDI monomer on a thin film device under a vacuum of 0.4 mbar and at160° C. with a throughput of 900 g/hour for the first pass and 250g/hour for the second pass.

960 g of a composition formed of biuret of hexamethylene diisocyanate(HDI) and of aminopropyltriethoxysilane (APTEO) are recovered, i.e. ayield of the order of 45%.

The NCO content is 0.364 (i.e., approximately 15.3%) and the viscosityis 2575 mPa·s at 25° C.

The silicon content is 3% by weight.

The proton NMR analysis in CDCl₃ medium gives the following distributionof the functional groups:

Moles % by Units of units weight of units Sum of the HDI units 100 74.4including carbamate 1.3 1.4 including allophanate 0.3 0.5(EtO)₃Si(CH₂)₃—N— unit 26 23.6

The distribution of the biuret units is as follows and is measured withregard to the following signals of the NH groups (at 7.5, 7.0 and 6.7ppm).

Units Chemical shift % HDI/(EtO)₃Si(CH₂)₃—N— 7.5 ppm 49 mixed biuretTrue HDI biuret 7.0 ppm 39 Urea 6.7 ppm 12

The true HDI biuret unit is composed of three hexamethylene chainsbonded to the biuret unit via the nitrogens.

The mixed biuret is composed of two hexamethylene chains of the HDI andof a propyltriethoxysilane chain which are bonded to the biuret unit viathe nitrogens.

A composition is thus obtained which is composed of biuret isocyanateoligomers with different degrees of polymerization composed of HDI andAPTEO biuret oligomeric compounds, of true HDI biuret oligomers and ofcompounds composed of a sequence of true HDI biuret and of HDI and APTEObiuret.

The functionality of isocyanate functional group is thus slightlygreater than 3 insofar as, during the process, there was formation oftrue HDI biuret, which is trifunctional.

Example 2 Biuret of Hexamethylene Diisocyanate (HDI) and ofAminopropyltrimethoxysilane (APTMO) (CMI 1489)

The procedure is as for example 1, except that APTMO is used instead andin place of APTEO.

An NCO/NH₂ molar ratio of 10 is used. 1680 g of HDI and 370 g of APTMOare used.

The viscosity of the final composition after distillation of HDI is 3980mPa·s at 25° C. and the NCO content is 0.356, i.e. 15%. The siliconcontent is 3.8%.

The yield recovered is 45%, i.e. 924 g of final composition, whichexhibits the following characteristics.

The proton NMR analysis in CDCl₃ medium gives the following distributionof the functional groups:

Moles % by weight Units of units of units Sum of the HDI units 100 70.2including carbamate 4.2 4 including allophanate 0.7 1.2(EtO)₃Si(CH₂)₃—N—unit 28.7 24.6

The distribution of the biuret units is as follows and is measured withregard to the following signals of the NH groups (at 7.5, 7.0 and 6.7ppm).

Units Chemical shift % HDI/(EtO)₃Si(CH₂)₃—N— 7.5 ppm 59 mixed biuretTrue HDI biuret 7.0 ppm 30 Urea 6.7 ppm 11

Example 3 Biuret of Hexamethylene Diisocyanate (HDI) and ofAminopropyltrimethoxysilane (APTMO) (CMI 1539)

The procedure is as for example 2 with regard to the same amounts ofproducts but slightly modifying the operating conditions; in particular,the heating time is 3 h instead of 2 h.

927 g of product, i.e. a yield of 45%, are obtained, with an NCO contentof 0.342, i.e. 14.4%, and with a viscosity of 5420 mPa·s at 25° C. Thesilicon content is 3.5%.

It is found that the process is reproducible.

Example 4 Biuret of Hexamethylene Diisocyanate (HDI) and ofAminopropyltrimethoxysilane (APTMO) (CMI 1478)

The procedure is as for examples 2 and 3, except that the batch isseparated into two before distillation of the monomer. 1010 g of productare purified by distillation of the HDI monomer.

430 g of product, i.e. a yield of 42.55%, are obtained, with an NCOcontent of 0.347, i.e. 14.6%, and with a viscosity of 5090 mPa·s at 25°C. The silicon content is 2.5%.

The proton NMR analysis in CDCl₃ medium gives the following distributionof the functional groups:

Units Moles of units % by weight of units Sum of the HDI units 100 70.5including HDI and 2.7 2.2 monomethyl carbamate including HDI and 0.6 0.9methyl allophanate (EtO)₃Si(CH₂)₃—N—unit 29.7 25.5

The distribution of the biuret units measured with regard to thefollowing signals of the NH groups (7.5, 7.0 and 6.7 ppm) is as follows:

Units Chemical shift % HDI/(EtO)₃Si(CH₂)₃—N— 7.5 ppm 63 mixed biuretTrue HDI biuret 7.0 ppm 28 Urea 6.7 ppm 9

The analysis of the oligomeric distribution by gel permeation gives thefollowing distribution:

Entities % by weight HDI monomer and NCO-propyltrimethoxysilane 0.2 HDIand monomethyl carbamate 0.4 True HDI dimer 1 HDI and monomethylallophanate 0.6 True 2 HDI/1 (EtO)₃Si(CH₂)₃—NH—mixed biuret 37.4HDI-true 2 HDI/1 (EtO)₃Si(CH₂)₃—NH—mixed 1.8 biuret dimer Mixed (3 HDI-2(EtO)₃Si(CH₂)₃—NH—) bis biuret 23.2 Mixed (4 HDI-3 (EtO)₃Si(CH₂)₃—NH—)tris 16 biuret + true HDI biuret sequence Mixed (4 HDI-3(EtO)₃Si(CH₂)₃—NH—) heavy 19.4 biuret + true HDI biuret sequence

Example 5 Biuret of Hexamethylene Diisocyanate (HDI) and ofAminopropyltriethoxysilane (APEMO) (CMI 1460)

The procedure is as for example 1, except that the NCO/NH₂ ratio is 7.

765 g of HDI and 287 g of APETO are employed.

After purification, 571 g are obtained, i.e. a yield of 55%.

The NCO content is 0.317, i.e. 13.3%, and the viscosity is 6790 mPa·s at25° C. The silicon content is 3.5%.

The analysis of the oligomeric distribution is presented in the tablebelow.

02CMI146002 foot HDI <0.1 HDI and ethyl carbamate 0.3 True HDI dimer(trace of 0.5 carbamate) Mixed biuret (trace of trimer 30.0 functionalgroup) Mixed bis biuret (trace of 24.1 dimer and trimer functionalgroup) Mixed tris biuret (trace of 16.5 dimer and trimer functionalgroup) Heavy product (mixed tetra 28.6 biuret) (trace of dimer andtrimer functional group)

Example 6 Biuret of Hexamethylene Diisocyanate (HDI) and ofAminopropyltriethoxysilane (APEMO) (CMI 1459)

The procedure is as for example 1, except that the NCO/NH₂ ratio is 10.

840 g of HDI and 221 g of APETO are employed.

After purification, 466 g are obtained, i.e. a yield of 44%.

The NCO content is 0.359, i.e. 15%, and the viscosity is 2850 mPa·s at25° C. The silicon content is 3.35%.

The process is reproducible.

The analysis of the composition is presented in the table below.

02CMI145902 foot HDI <0.1 HDI and ethyl carbamate 0.3 True HDI dimer 1.2Mixed biuret (trace of trimer 38.4 functional group) Mixed bis biuret(trace of 27.0 dimer and trimer functional group) Mixed tris biuret(trace of 14.9 dimer and trimer functional group) Heavy product (mixedtetra 18.2 biuret) (trace of dimer and trimer functional group)

Example 7 Composition Formed of Polybiuret and PolyisocyanurateComprising Trialkoxysilane Functional Group (CMI 1479)

1010 g of composition from example 4 are introduced into a 3 l reactorequipped with a mechanical stirrer, dropping funnels and a refluxcondenser and rendered inert with nitrogen. The NCO content of thereaction medium is 30% (0.716 NCO per 100 g). The reaction medium isbrought to 110° C. and 10 g of hexamethyldisilazane (10% by weight) areintroduced with stirring. The temperature of the reaction medium isbrought to 140° C. over 50 minutes and this temperature is maintainedfor 3 hours. The degree of conversion of the NCO functional groups isregularly measured. It changes as follows: 8.9% at the end of 1 hour ofreaction after addition of HMDZ, 10.6% after 1 h 30, 14.8% after 2 h 30and 16.8% after 3 hours. The reaction medium is cooled to 100° C. over25 minutes and 4.6 g of 1-butanol are added to the reaction medium inorder to halt the cyclotrimerization reaction. The reaction medium issubsequently purified to remove the excess monomer. The samepurification method as that described in example 1 is used.

484 g of composition formed of polybiuret polyisocyanurate comprisingalkoxysilane units are obtained, i.e. a yield of 47%.

The NCO content is 0.369, i.e. 15.5% by weight. The viscosity is 11 800mPa·s at 25° C.

The oligomeric distribution of the composition thus obtained ispresented below.

% by Entities weight HDI monomer and NCO-propyltrimethoxysilane 0.2 HDIand monomethyl carbamate 0.4 Isocyanatopropyltrialkoxysilane andmonomethyl 0.3 carbamate True HDI dimer 1.8 HDI and monomethylallophanate 2 Mixture of true 2 HDI/1 (EtO)₃Si(CH₂)₃—NH— mixed 32.3biuret and of true isocyanurate trimer of HDI and of true isocyanuratetrimer of HDI and of isocyanato- propyltrialkoxysilane HDI-true 2 HDI/1(EtO)₃Si(CH₂)₃—NH— mixed biuret 3.7 dimer Mixed (3 HDI-2(EtO)₃Si(CH₂)₃—NH—) bis biuret and 19.3 mixed (3 HDI-2(EtO)₃Si(CH₂)₃—NH—) biuret - and comprising isocyanurate and dimer unitsHeavy products composed of mixed (4 HDI-3 40 (EtO)₃Si(CH₂)₃—NH—) biuretand true HDI biuret sequences and comprising isocyanurate, dimer,carbamate and allophanate units* *see below an example of structuresformed of sequences comprising biuret and isocyanurate units comprisingalkoxysilane units.

The proton NMR analysis in CDCl₃ medium gives the following distributionof the functional groups:

Units Moles of units % by weight of units Sum of the HDI units 100 70.2including HDI and 4.5 3.7 monomethyl carbamate including HDI and 2.9 4.5methyl allophanate including HDI 8.4 5.9 isocyanurate units(EtO)₃Si(CH₂)₃—N— unit 16.8 14.4 Sum of the units 3.6 1.1 resulting fromthe butanol (carbamate allophanate)

The distribution of the biuret units, measured with regard to thefollowing signals of the NH groups (7.5, 7.0 and 6.7 ppm), is asfollows:

Units Chemical shift % HDI/(EtO)₃Si(CH₂)₃—N— 7.5 ppm 39 mixed biuretTrue HDI biuret 7.0 ppm 50 Urea 6.7 ppm 11

Nonlimiting example of structures formed of sequences comprising biuretand isocyanurate units comprising alkoxysilane units

Examples 8 to 10 Examples of the Functionalization of the Silane BiuretCompounds Example 8 Polyurethane Polydimethylsiloxane PolybiuretPrepolymer Comprising Trialkoxysilane Functional Groups (CMI 1488)

100 g of a composition of example 1 and 182 g of a telechelic siliconeoil comprising 2 hydroxypropyl functional groups (Rhodorsil V75) arecharged to a reactor. The content of isocyanate functional groups is0.129.

The NCO functional groups/OH functional groups molar ratio is 2.

The mixture is heated to 80° C. and the content of isocyanate functionalgroups is monitored. It changes in the following way:

-   -   after reacting for 2 h 40, the content is 0.113, i.e. a        consumption of NCO functional groups of 12.4%,    -   after reacting for 4 h, the content is 0.097, i.e. a consumption        of NCO functional groups of 24.8%,    -   after reacting for 9 h at 80° C., the NCO content is 0.066        (2.77%), i.e. a degree of conversion of 49%.

A composition formed of polyurethane polydimethylsiloxane polybiuretprepolymer comprising pendant trialkoxysilane functional groups with anNCO content of 2.77% is thus obtained. The product is a viscous liquid.

This product is used as adhesion primer for silicone mastics.

Example 9 Polyurethane Polybiuret Comprising Trialkoxysilane FunctionalGroups (CMI 1491)

The isocyanate functional groups of a compound of example 2 are blockedby methanol in order to obtain the corresponding methyl carbamate.

100 g of a composition of example 2 and 11.5 g of methanol areintroduced into a reactor. The NCO content is 3.320 and the NCO/OH ratiois 1.

The mixture is heated at 60° C. for 4 h. The NCO content measured is0.055. After a further 6 h at 80° C., the NCO content is 0.017 mol ofNCO per 100 g, i.e. 0.71%.

A composition formed of polybiuret comprising trialkoxysilane functionalgroups polymethyl carbamate is obtained.

These compounds can be used to be crosslinked with melamines and makepossible better attachment of the pigments to the network thus obtained.

Example 10 Polyurea Polybiuret Comprising Mixed TrialkoxysilaneFunctional Groups (CMI 1491)

100 g of example 1 are charged to a reactor and then 67.3 g ofaminopropyltrimethoxysilane are added over 15 minutes. The NCO/NH₂ ratiois equal to 1. The content of NCO functional group is 0.218.

The reaction is exothermic and the temperature of the reaction mediumrises to 100° C. After reacting at 80° C. for 3 hours, the content ofNCO functional groups is 0.

The reaction mass is subsequently withdrawn at 100° C.

After cooling, the composition obtained gives a nonsticky off-whitepaste.

Example 11 Polybiuret Comprising Mixed Trialkoxysilane Functional Groupsand Comprising Acrylic Units and Comprising Isocyanate Functional Groupswhich are Free (CMI 1491)

This composition is a composition of use for systems comprising athreefold crosslinking system:

-   -   crosslinking via isocyanate functional groups with polyol or        polyamine compounds comprising a mobile hydrogen,    -   crosslinking by a radiative technique (crosslinking under UV        radiation or electron gun) with other crosslinkable monomers        possessing double bonds,    -   crosslinking with silanol or hydroxyl functional groups of        inorganic materials (silica, titanium dioxide, zirconia) or        alkoxysilanes.

These systems are therefore advantageous for acting as coupling agentsbetween an inorganic material and an organic material.

100 g of composition of example 1 (NCO content of 0.364 mol of NCO per100 g), 14.1 g of hydroxyethyl acrylate (HEA), i.e. 0.121 mol, and 114mg of BHT (2,6-bis(tert-butyl)-4-methylphenol, i.e. 1000 ppm withrespect to HEA) are introduced into a reactor.

The mixture is heated at 80° C. for 12 hours.

The NCO content is measured and changes as follows:

-   -   after 2 h 30, the NCO content is 0.266, i.e. a degree of        conversion of NCO of 16.6%,    -   after 4 h 30, the NCO content is 0.239, i.e. a degree of        conversion of NCO of 25.1%,    -   after 6 h, the NCO content is 0.227, i.e. a degree of conversion        of NCO of 29%,    -   after 11 h, the NCO content is 0.219, i.e. a degree of        conversion of NCO of 31.3%,    -   after 12 h, the NCO content is 0.215, i.e. a degree of        conversion of NCO of 32.6%.

The calculated theoretical NCO content is 0.213 mol of NCO per 100 g.

The reaction is thus halted and the composition thus obtained is aliquid composition which exhibits a content of NCO functional group of9% and a silicon content of 2.6%.

One of the compounds of the composition obtained can thus be written asfollows:

Comparative Example 1

100 g of Tolonate HDT (HDI polyisocyanurate sold by Rhodia) with acontent of NCO functional groups of 0.52 mol per 100 g are introducedinto a reactor equipped as in example 1.115 g ofaminopropyltriethoxysilane (i.e. 0.52 mol) are run in over 1 hour. TheNCO/NH₂ ratio is 1.

An immediate precipitation of urea formed from Tolonate HDT and fromaminopropyltriethoxysilane is observed, with release of a considerableamount of heat. The mixture becomes difficult to stir.

The product is a solid which is difficult to handle and which is notvery soluble in organic solvents, such as Solvesso or esters.

Comparative Example 2

The procedure is as for comparative example 1, except thataminopropyltrimethoxysilane (93 g) is used as silane. Compounds are thusobtained which precipitate and which are sparingly soluble in organicsolvents.

Applicational Results Obtained with the Compounds of the Invention

The compounds of the invention have been used with success in 4 fieldsof application:

-   -   coatings, paints and varnishes,    -   silicone mastics and adhesion primers on various surfaces,    -   heavy-weight tires,    -   polyamide fiber coatings.

1. A process for the preparation of an isocyanate composition comprisingbiuret functional groups, comprising the steps of (a) reacting at leastone isocyanate monomer with an aminoalkylsilane to form anisocyanatoalkylsilane and (b) reacting the isocyanatoalkylsilane with anisocyanate to form a biuret, where the amino portion of theaminoalkylsilane unit in the isocyanate composition is an amino group ofthe biuret.
 2. The process as claimed in claim 1, wherein at least 5% ofbiuret functional groups not carrying a silanoalkyl chain are formedwith respect to the combined biuret functional groups in thecomposition.
 3. The process as claimed in claim 1, wherein, expressed asequivalents, the ratio of the isocyanate functional groups to the numberof hydrogens carried by the amine functional groups is at least
 4. 4.The process as claimed in claim 1, wherein at least 10% of biuretfunctional groups not carrying a silanoalkyl chain are formed withrespect to the combined biuret functional groups.
 5. The process asclaimed in claim 1, wherein, expressed as equivalents, the ratio of theisocyanate functional groups to the number of hydrogens carried by theamine functional groups is at least 8.